Well tools



July 9, 1968 T. L. ELLISTON WELL TOOLS 2 Sheets-Sheeti Filed Dec. 8. 1964 INVENTOR Thomas L. Elliston @W WW0? ATTORNEYS Fig. I

United States Patent Engi- Tex., a corporation of ABSTRACT OF THE DISCLOSURE A packer having sealing means disposed between oppositely facing anchoring means to be anchored in a flow conductor, and having stress control means associated with the packing sleeve or seal element and the anchoring means to control the stress set up in the seal element prior to setting of both sets of anchoring means, providing for build-up and maintenance of high compression stresses in the seal element during setting of the second set of anchoring means.

This invention relates to well tools and more particularly to well tools having expansible sealing means.

It is an object of this invention to provide a new and improved well tool for effecting a seal in a well bore with an expansible element.

It is another object of this invention to provide a new and improved well tool for closing the annulus between an inner flow conductor and an outer flow conductor in which the inner flow conductor is disposed.

It is another object of the invention to provide a well tool for effecting a seal in the annular space within a well bore around either single tubing strings or multiple tubing strings.

It is another object of the invention to provide a well tool including an expandible resilient seal element which after the tool is set will withstand a pressure differential across the seal element greater than can be withstood by conventional well sealing tools. 7

It is a most important object of the invention to provide a well tool having setting means including control means which permit stresses to be induced in the seal element during initial setting in excess of the stresses obtainable in conventional forms of tools having well sealing means.

It is another object of the invention to provide a well tool with expansible sealing means which is subjected to a predetermined stress prior to locking the tool in a well bore.

It is an important object of this invention to provide a well sealing tool in which a first set of slips is set and an expandible seal element is expanded under predetermined stress conditions prior to setting a second set of slips.

It is another object of the invention to provide a well tool having upper and lower slips and an expandible seal element.

It is a still further object of the invention to provide a well tool in which a predetermined stress is built up in the expandible seal element before the lower slips can be expanded into engagement with the wall of the well bore.

It is another object of the invention to provide a well packer utilizing yieldable means which resists the setting of the lower slips until full expansion of the seal element, thereby permitting a predetermined load to be imposed on the seal element until the yield point of such means is reached at which time the lower slips will set and lock the seal element in sealing relationship under maximum stress conditions.

It is a still further object of the invention to provide a well packer in which the seal element is stressed to a predetermined value without abrupt relaxations of the force applying the load to the seal element.

It is another object of the invention to provide a well packer in which the seal element is stressed under constantly increasing load conditions which reach a substantially level predetermined value during the setting of the slips thus avoiding abrupt relaxations of the seal element which would make the elements susceptible to leakage after setting of the packer.

It is still another object of the invention to provide a well packer having a seal element which maybe set under maximum predetermined stress conditions without the necessity of additional stressing of the seal element subsequent to setting of the packer thus avoiding dragging the slips against the inner wall of the well bore.

It is a still further object of the invention to provide a well packer in which the seal element is expanded and locked without sudden relaxations which tend to prematurely set the slips and prevent full expansion of the seal element.

It is another object of the invention to provide a well packer which does not prematurely set the slips necessitating dragging the slips along the casing wall to effect further seal element expansion.

Additional objects and advantages of the invention will be readily apparent from the reading of the following description of a device constructed in accordance with the invention, and reference to the accompanying drawings thereof, wherein:

FIGURE 1 is a longitudinal view partially in elevation and partially in section of a single string form of packer constructed in accordance with the invention;

FIGURE 2 is a view in section along the line 2-2 of FIGURE 1;

FIGURE 3 is a view in section along the line 3-3 of FIGURE 1;

FIGURE 4 is a longitudinal view partially in section and par-tially in elevation illustrating the well packer of FIGURE 1 set within a well casing with the seal element expanded into contact with the well casing and the slips expanded into locking engagement with the casing;

FIGURE 5 is a longitudinal view partially in elevation and partially in section illustrating a multiple string well packer constructed in accordance with the invention;

FIGURE 6 is a view in section along the line 66 of FIGURE 5;

FIGURE 7 is a longitudinal view partially in elevation and partially in section illustrating the well packer of FIGURE 3 set in a well casing with the seal element expanded into contact with the well casing and the slips in locking engagement with the inner surface of the casing; and

FIGURE 8 is an enlarged fragmentary sectional view of the lower slip cone and slip carrier of the packer of FIG- URE 5, showing a modified form of the stress control means for maintaining the seal element expanded during setting of the lower slips.

Referring to FIGURES 1, 2 and 3, the single string packer 9 constructed in accordance with the invention includes a tubular shaped mandrel 10 which supports an annular flexible seal element 11, an upper slip assembly 12, and a lower slip assembly 13. The head member 14 is secured to the upper end of the mandrel. As illustrated, the packer is adapted to be run into and disposed in a well casing 15 by means of a suitable running tool schematically shown to be a running tool 20.

The head member 14 is a tubular shaped member having a longitudinal bore 21 and provided with internal threads 22 in the lower portion of the bore for engagement with the upper end of the mandrel. The head is provided with a first internal annular flange 23 for connection of the running tool and a second internal annular flange 24 forming a shoulder 25 to engage the upper end of the mandrel. In FIGURE 1, the running tool 20 is illustrated in engagement with the head member with the external sleeve 30 of the running tool positioned over the head while the internal member 31, which may be a collet, is positioned within the bore in engagement with the internal annular flange 23. The collet 31 has resilient fingers 32 provided with bosses 33 each of which has an upwardly facing sloping surface 34 and a downwardly sloping surface 35, the sloping surfaces functioning in connection with engaging and disengaging the running tool. The collet and sleeve of the running tool are longitudinally movable relative to each other. Any suitable running tool may be utilized for setting the packer one of which is illustrated in the patent to Bonner, No. 3,160,209. The draw bar of the setting tool is connected to the collet member 31 of the running tool and the cylinder of the setting tool is connected to the sleeve 30 of the running tool, whereby the draw bar of the setting tool will pull the collet upwardly and the sleeve 31 will hold the packer parts therebelow abutting the lower end thereof against movement during the setting operation which will be hereinafter more fully explained.

The mandrel is provided with an internal longitudinal bore 10a and with the external threads 40 along a section near the upper end thereof to cooperate with the threads 22 of the head for engaging the mandrel within the head member. The lower portion of the mandrel is provided with a section 21 of reduced diameter which provides a downwardly facing external annular shoulder 42 on the mandrel. The lower external surface of the mandrel is threaded along a section 43.

An upper slip carrier 44 is secured around the mandrel 'below the threads 40 by a shear pin 45. A plurality of slips 50 are dependent at their upper ends from the upper slip carrier and are held around the mandrel in engagement with the slip carrier by a breakable or expandable band 51. An upper slip cone 52 having an upwardly and inwardly sloping surface 52a is secured on the mandrel below the upper slips by the shear pin 53. Both the upper slip carrier and the upper cone are fitted in sliding relationship around the mandrel so that when their respective pins are sheared they may slide along and relative to the mandrel and to each other.

The seal element 11 is an annular member fitted around the mandrel and formed of a resilient rubber-like material which may 'be stressed by forces exerted at opposite ends of the element to effect lateral expansion so the element will form a seal in the annulus between the external surface of the mandrel and of the internal surface of the casing 15. The seal element is confined between an upper 'back up shoe 54 and a lower back up shoe 55. Each of the back up shoes is constructed of a deformable metal such as brass which will shape upon contact with the inner surface of the casing to conform to the configuration of the surface. The back up shoes function to prevent extrusion of the seal element.

A lower slip cone 60 is slidably positioned on the mandrel below the seal element. The lower cone has an enlarged 'bore along a section 61 at the lower end of which is an internal annular shoulder 62 within the cone. The external annular shoulder 42 on the mandrel and the internal annular shoulder 62 within the lower slip cone are engageable with each other as illustrated in FIGURE 1. The extenral surface of the mandrel has a section 620 which is an inwardly and downwardly sloping surface for expansion of the lower slips. A plurality of lower slips 63 are secured around the lower cone by an expandable or breakable band 64. The lower slips are engaged at the lower ends thereof around the lower slip carrier 65 the upper end of which is fitted in sliding engagement over the lower end of the lower cone. The bore of the lower slip carrier is enlarged along the portion 70 so that an annular cylinder 70a around the mandrel is defined by the external surface of the mandrel and the lower portion of the lower slip cone on the inside and the internal surface of the lower slip carrier within the bore 70 on the outside. The lower slip carrier is internally threaded along a portion 71 in the lower section of the bore 70.

An annular shaped die member 72 provided with both internal and external threads around the upper portion is engaged in the lower end of the lower slip carrier and around the lower end of the mandrel. The die member is provided with the internal threads 73 and the external threads 74. The internal threads 73 engage the threads 43 on the mandrel and external threads 74 engage the threads 71 within the lower slip carrier. The die member is provided with an internal bore 75 which communicates with the bore 10a through the mandrel to provide a continuous unobstructed flow passage through the packer. A plurality of radially spaced longitudinal bores 80, as in FIGURES 1 and 3, extend through the die member with the upper ends of the bores being reduced in diameter at 81 where the bores open into the annular cylinder 70a. An annular piston 82 is positioned within the cylinder. The piston has an enlarged bore 83 which terminates in an internal annular shoulder 84 to engage the lower end of the lower slip cone. An annular body or charge 90 of extrudable material, such as lead, is disposed within the annular cylinder between the upper end of the die member and the lower end of the piston 82. As will be explained hereinafter, the material 90 resists relative movement toward each other of the piston and the die member until the yield pressure of the material is attained at which time the material is extruded through the die portions 81 of each of the bores to be expelled from the die member through the bores. The resistance to extrusion provided by the material furnishes the force which opposes setting of the lower slips while permitting a steady, gradual expansion of the seal element.

FIGURE 4 illustrates the packer set within the well casing 15 and the seal element expanded into sealing relationship with the internal surface of the casing. The setting of the packer is achieved by the following procedure. The packer is engaged on a suitable running tool 20 by securing the running tool to the head of the packer, as illustrated in FIGURE 1. The collet 31 of the running tool is inserted into the bore of the head until the collet fingers 32 snap inwardly and slide past the annular internal flange 23 with the upwardly facing shoulders 34 of the collet finger bosses engaging the lower end of the flange. The sleeve 30 of the running tool fits around the head with the lower end of the sleeve in engagement with the upper end of the upper slip carrier 44. The packer is then lowered through the casing to a desired location whereupon the setting tool is actuated so that the collet of the running tool is lifted while its sleeve 30 is maintained stationary. The collet pulls the head of the packer and the mandrel upwardly relative to the outer sleeve 30. Since the lower end of the sleeve engages the upper end of the slip carrier 44, movement of the mandrel relative to the upper slip carrier results in fracturing the shear pins 45 to free the mndrel to move upwardly relative to the slip carrier. The inward end 45a of the shear pin remains in the mandrel, as shown in FIGURE 4. After the shear pin 45 is fractured the mandrel is moved in an upward direction relative to both the slip carrier and slips causing the upper slip cone 52, by virtue of its shear pin connection with the mandrel, to be carried upward beneath the upper slips which are being held stationary by the upper slip carrier. Upward movement of the upper cone beneath the upper slips expands the slips outwardly causing the band 51 to fracture or expand to allow the slips to move into locking engagement with the inner surface of the well casing. When the upper slips are engaged with the inner surface of the casing, the upper slip cone becomes wedged between the slips and the mandrel preventing farther upward movement of the cone. Since the mandrel is still being urged in an upward direction by the setting tool, the shear pin 53 securing the cone to the mandrel fractures to allow continued upward movement of the mandrel. The reference numeral 53a designates the inward end of the shear pin 53 after fracture and movement of the upper cone. Upward movement of the mandrel also causes the die member 72, due to its threaded engagement with the lower end of the mandrel, to be pulled in an upward direction. The upper end of the die member pushes against the lower end of the material 90 within the annular cylinder. The material 90 in turn transmits the force to the lower end of the annular piston 82. The piston 82 which is engaged through the shoulder 84 with the lower end of the lower slip cone moves the cone in an upward direction. The lower back up shoe 55 rests on the upper end of the lower cone and thus upward movement of the cone forces the lower back up shoe in an upward direction. Thus, upward movement of the mandrel through the medium of the extrudable material in the cylinder 70a forces the lower end of the seal element upwardly. Upward movement of the lower back up shoe causes the lower end of the seal element to be forced in an upward direction toward the upper end of the seal element which is held against upward movement by the upper slip assembly which is now anchored against upward movement in the casing. As the lower end of the seal element is driven upwardly relative to the upper end of the seal element, the seal element is stressed effecting lateral expansion of the element toward the casing of the well. So long as the lower back up shoe and thus the lower end of the seal element is urged in an upward direction the stress will increase within the element to effect a tighter sealing relationship between the mandrel and the well casing.

As long as the die member is urged upwardly by the mandrel the die member acting through the extrudable material will urge the lower cone in an upward direction. Since the extrudable material is an integral link between the mandrel and the lower cone the extrudable material will press the lower cone in an upward direction until the yield point of the extrudable material is reached. When the yield point of the extrudable material is reached, the material will begin to behave as a semi-liquid and be forced through the bores 81 in the die member. With the force on the die member causing extrusion of the material 90 through the bores 81 and thus displacement of the material from the cylinder, the mandrel and die member may move upwardly relative to the annular piston and lower slip cone causing upward movement of the lower slip carrier. As the lower slip carrier moves in an upward direction it forces the lower slips along the sloping surface 62a of the slower slip cone causing their outward expansion and a fracturing or expansion of the band 64 to allow the lower slips to move into locking engagement with the well casing. Throughout the period beginning at the time the extrudable material starts to extrude through the die member and concluding with the setting of the lower slips the force necessary to cause extrusion of the material is continually exerted on the lower end of the seal element since the lower end of the lower cone is engaged with the annular piston which is being pressed upon by the extrudable material as it is being extruded. Since, for continued extrusion of the material, it is always necessary that it be stressed beyond its elastic limit there is no time during the setting of the lower slips that the force on the packer seal element is at a level below that necessary to maintain the material at least at its elastic limit in compression. The bores 80 are slightly larger than the die bores 81 in order to reduce the frictional force resisting the flow of the extruded material since the actual extrusion occurs within the bores 81. When the lower slips are fully engaged with the well casing the lower cone will be wedged between the mandrel and the lower slips to prevent any relaxation of the packer seal element. Since the seal element was set at the pressure necessary to extrude the material 90 it is fully engaged in sealing relationship with the mandrel and the well casing to prevent leakage due to a pressure differential across the element.

With the packer fully set within the casing the running tool may be disengaged from the packer and withdrawn from the casing. Since the lower slips are set, the mandrel is held against upward movement due to the Wedging effect of the slips between the lower cone and the casing. An upward force is applied to the running tool causing the collet fingers 32 to be pushed inwardly due to the surface 34 on the bosses 33 striking the lower end of the flange 23. The collet fingers spring inwardly and the bosses pass the flange freeing the running tool which is then withdrawn from the casing.

An application of the invention to a dual string packer is illustrated in FIGURES 5, 6 and 7. Referring particularly to FIGURE 5, the packer comprises the mandrels 101 and 102 which support a seal element 103, an upper slip assembly 104, a lower slip assembly 105 and a head member 110. Each of the mandrels is a hollow tubular member the bore of which functions as a flow passage through the mandrel. The head member is provided with two bores which register with the bores of the mandrels 101 and 102 to provide two continuous flow passages through the packer. Only the bore 111 interconnecting with the mandrel 102 is illustrated in the drawings. The head member is provided with the lugs 112 and 113 to facilitate connection of a suitable running tool to the packer. Each of the bores of the head member is internally threaded to permit engagement of the upper end of each of the mandrels in the head member. For example, the bore 111 is internally threaded at 114 for connection of the upper end of the mandrel 102. The head member is also provided with a ring seal 115 for effecting a sealing relationship between the head member and the upper end of the mandrel 102. An internal annular flange 116 provides a shoulder 117 within the bore 111 to engage the upper end of the mandrel 102. In the bore of the head member which interconnects with the mandrel 101 the head member is similarly internally threaded and provided with a ring seal and an annular flange, not shown, to provide connecting and sealing means between the head member and the mandrel 101.

An upper slip carrier 120 is slidably positioned around the mandrels and secured to the mandrels by shear pins 121. A plurality of upper slips 122 are supported from the upper slip carrier and secured around the carrier and the mandrels by an expandable or breakable band 123 which maintains the slips in retracted position and assists in achieving uniform contact with the casing wall upon expansion of the slips. An upper slip cone 124 is slidably engaged around the mandrels below the upper slips and secured to the mandrels by the shear pins 125. The upper cone is provided with a plurality of upwardly and inwardly sloping grooves along which the slips slide to expand into contact with the well casing.

The seal element 103 is slidably engaged around the mandrels below the upper slip cone. The seal element is confined between an upper back-up shoe 131 and a lower back-up shoe 132. Each of the back-up shoes is constructed of a deformable metal which will conform to the inner surface of the casing to prevent extrusion of the seal element when it is expanded. The back-up shoes may be formed of a soft brass. The seal element is constructed of a rubber-like material which will expand laterally when subjected to compressive stress effected by application of forces to the opposite ends of the element pushing the ends toward each other. The seal element expands laterally to establish a leak proof seal in the annular space around the mandrels between the mandrels and a well casing 15, as shown in FIGURE 7.

The lower slip cone is slidably engaged around the mandrels below the seal element. The lower cone is provided with a first bore 140:: to receive the mandrel 102 and a second bore, not shown, for the mandrel 101. The bores of the cone are enlarged along a section, section 141, for example, in the bore 140, extending from the upper end of the cone to allow the cone to slide over a lock ring 142 engaged around each of the mandrels. The cone is provided with a plurality of downwardly and inwardly sloping external grooves 143 used in expansion of the lower slips. Slidably engaged in each of the grooves 143 around the lower cone is a lower slip 144- which is provided with a plurality of external teeth 144a for gripping the internal surface of a casing. The lower slips are retained around the mandrels and lower cone by an expandable or breakable band 145 which assists in establishing uniform contact between the teeth of the slips and the surface of the casing in which the packer is set. A lower slip carrier 150 is engaged around each mandrel below the lower slips. The longitudinal position of the slip carrier is maintained by the upper lock ring 151, which is secured arounnd the mandrels and fits in a short enlarged bore section 152 of the slip carrier and a lower lock ring 153 secured around each mandrel below the slip carrier. While only the mandrel 102 is shown in section to illustrate the lock rings, it is to be understood that the mandrel 101 is similarly fitted with lock rings engaged with the lower slip carrier. The lower end of each of the lower slips is operatively engaged in a conventional manner over the lower slip carrier whereby upward movement of the carrier will push the lower slips upwardly and outwardly along the sloping grooves 143 in the lower slip cone.

The stress within the seal element when the lower slips are set and locked in the well casing is controllable at a predetermined value by mechanism and procedure substantially the same as that above described with respect to the single string packer illustrated in FIGURES l and 2. Referring again to FIGURE 5, the lower slip cone is provided with a plurality of cylinders 160 opening through the lower end of the cone. Preferably an equal number of the cylinders are formed in the lower cone evenly distributed on opposite sides of the mandrels. For example, if two cylinders are employed, as illustrated in the drawings, there shcould be one on each side of the two mandrels. An even number of cylinders is desirable to achieve mechanical balance in operation of the packer. The lower slip carrier is provided with a plurality of bores 161 which are equal in number to the cylinders 160 and so positioned in the slip carrier that the longitudinal axis of each of the bores in the carrier will be coincident with the longitudinal axis of a corresponding cylinder in the lower cone. The positions of the bores of the slip carrier relative to the locations of the mandrels are best illustrated in FIGURE 6'. Each of the bores 161 is enlarged along a section 162 which terminates in a shoulder 163. A die 164 is secured in each of the bores 161 of the lower slip carrier. The lower portion of each of the dies is fitted within the enlarged bore section 162 of each of'the bores through the carrier with the lower end of each die engaging a shoulder 163. Each die has a graduated bore comprising a die section 165 at the upper end and a larger section 170 which combine to provide a continuous passage through the die. The external surface of each die in that portion which extends above the lower slip carrier is of a diameter which will form a tight sliding fit with the the corresponding cylinder 160 in the lower cone so that the die may slide upwardly into the cylinder. It may be considered that the die functions both as a piston and a die for reasons which will be explained hereinafter. A charge of extrudable material 171, which may be lead, is positioned in each cylinder 160 above the corresponding die to serve as a yieldable link between the carrier and cone. The material 171 is molded to conform to the shape of the cylinder. The enlarged portion 170 of the bore through the die member is provided to minimize frictional resistance to the flow of the extrudable material after it has been extruded through the die during the setting of the lower slips in accordance with the invention.

Connected to the lower end of the mandrel 101 is a coupling 180 in which is engaged a section of a tubing string 181. A coupling 182 is connected to the lower end of the mandrel 102 to secure a section of the tubing string 183 to the lower end of the mandrel. The tubing strings 181 and 183 extend downwardly to other equipment, not shown, within a well bore below the packer.

The packer is set within a well bore in the following manner. A suitable running tool, not shown, having an inner member provided with connecting means such as J-slots for releasably engaging the lugs 112 and 113 and an outer sleeve which will slide over the head to engage the upper slip carrier is secured to the head of the packer. The packer is then lowered on the running tool to the elevation within the well at which the packer is to be expanded and locked. When the running tool is at the desired elevation it is actuated to initiate the setting of the packer. The inner member of the tool secured to the lugs is raised while the sleeve is maintained stationary to hold the upper slip carrier down. The head and the mandrels are thus lifted upwardly relative to the sleeve of the running tool and since the sleeve of the tool is restraining the upper slip carrier from upward movement the shear pin 121 is fractured. FIGURE 7 shows the position of the inward end 121a of the shear pin 121 after the pin is sheared and the mandrel has moved upwwardly. After fracture of the shear pin the mandrels may slide upwardly relative to the upper slip carrier which still is being restrained by the sleeve of the running tool with the result that the upper slip cone 104 is moved in an upward direction beneath the upper slips. The sloping grooves of the upper cone force the upper slips outwardly causing expansion or fracturing of the band 123 to free the slips and allow them to be expanded by the cone into locking engagement with the well casing 15. When the upper slips are fully expanded into the casing wall the upper cone wedges between the inner surface of the slips and the mandrels, as in FIG- URE 7, stopping further upward movement of the upper cone. Since the upper cone can no longer move upwardly and an upward force is continuing to be applied to the mandrels by the running tool, the shear pins 125 are fractured to free the mandrels from the upper cone and permit their continued movement in an upward direction. The reference numeral 125a designates the inward end of a shear pin 125 after it is sheared and the mandrels have moved upwardly relative to the cone.

With the shear pins 125 fractured the mandrels continue movement in an upward direction. Since the lock ring 142 may slide upwardly within the enlarged bore section 141 of the lower slip carrier 142 there is no direct permanent longitudinal connection between the mandrels and the lower slip carrier which will cause the carrier to be moved in an upward direction with the mandrels. However, there is a connection between the mandrels and the lower slip carrier through the mechanism of the extrudable material 171. The lower cone is locked longitudinally on the mandrels by the rings 152 and 153. A die 164 is secured in each of the bores 162 in the lower slip carrier. The upper end of each of the dies engages the lower end of the charge of extrudable material 171 within each of the cylinders 162 providing a connection between the upper ends of each of the dies and the lower cone through the medium of the extrudable material. Thus, upward movement of the mandrels pushes the lower slip carrier in an upward direction forcing the dies toward the lower cone and against the lower end of the extrudable material. The extrudable material, so long as the force on it is below its compressive elastic limit, pushes the lower cone upwardly as the mandrels move upwardly. Since the upper end of the lower cone engages the lower back-up shoe 132, the lower end of the seal element 103 is pushed in an upward direction relative to the upper end of the slip element which is being restrained by the upper cone. As the lower end of the seal element is thus pushed upwardly relative to its upper end stress is set up in the element cfi'ccting its lateral expansion to fill the annular space between the mandrels and the inner surface of the Well casing. The upward movement of the mandrels is continued with a gradual increase in the stress being induced in the seal element until suflicient force is exerted on the material 171 by the upper ends of the dies 164 to cause it to be extruded from the cylinders through the bores 164 in the dies. The material '171 is displaced from the cylinders downwardly through the dies allowing the dies to move into the cylinders and thus in an upward direction relative to the lower cone. Since the dies are secured in the lower slip carrier the carrier moves in an upward direction pushing the lower slips along the grooves 143 to effect fracture or expansion of the band 145 and outward expansion of the slips into engagement with the well casing. Throughout the process of the setting of the lower slips there is a continued connection between the upper ends of the dies and the lower slip cone through the medium of the extrudable material. Though the material is being extruded through the dies it is capable of transmitting force to the lower cone to the value of its compressive elastic limit thus maintaining a constant force on the lower end of the seal element throughout the lower slip setting procedure. When the lower slips are set movement of the lower carrier and extrusion of the material 171 will cease and the material will continue to provide a connecting link between the lower slip carrier and the cone to prevent relaxations of the seal element which might force the cone in a downward direction. The engagement of the slips with the inner wall of the casing causes the lower cone to be wedged between the inner surface of the slips and the mandrels locking the lower slip cone in position to prevent any longitudinal movement. FIGURE 7, illustrates the packer 100 as fully set within the well casing with both the upper and lower slips engaging the inner wall of the well casing to lock the packer within the casing. The material 171 has been extruded to a great extent through the dies with the material flowing downwardly through the dies and into the bores 161 of the lower slip carrier thus evidencing displacement of the extrudable material to permit the relative movement between the lower slip carrier and the lower cone to allow setting of the lower slips while maintaining a uniform force between the carrier and the cone to prevent relaxation of the seal element. Since through the extrudable material there was a constantly increasing force on the lower end of the seal element reaching a maximum uniform value during the setting of the lower slips there is no sudden relaxation of the seal element as occurs in conventional packers which will tend to wedge the cone beneath the slips prior to achieving maximum stress within the seal element.

With the packer fully set in the casing the mandrels are held against upward movement by the lower carrier which is restrained by the wedging of the slips between the lower cone and the casing. The running tool inner members are lowered and rotated to disengage the J-slots of the tool from the lugs 112 and 113 to free the running tool. The tool is lifted from the packer and withdrawn from the casing.

It has been indicated that the extrudable material employed in each of the described embodiments of the invention preferably is lead. It has been found that lead confined in a chamber such as those disclosed in both packers of the present invention will act as a semi-liquid at an internal stress of approximately 19,250 p.s.i. and is readily displaced from the chamber through a die under such compressive stress. Where lead is to be used as the extrudable material the relationship between the cross-sectional area of the lead charge in the chamber and the area of the die openings may be determined in the following'manner. Assume that a unit stress of 2,500 psi. is desired in the packer seal element when a packer having a mandrel 5.00 inches in external diameter is set in 7 inch casing having an internal diameter of 6.004 inches. The axial loading which must be imposed on the end of the packer element is determined as follows:

10 s" s) where:

W=total axial load on the seal element in pounds;

S=the unit stress in the seal element in p.s.i.;

A =the cross-sectional area of the internal bore of the casing in square inches; and I a =the area described by the outside diameter of the packer mandrel at the center of the seal element in square inches (the expression A .,a may otherwise be stated to represent the cross-sectional area of the seal element when it has been laterally expanded into sealing relationship and thus fills the annular space between the external surface of the mandrel and the internal surface of the casing). The total longitudinal force which must be exerted on the example seal element is thus determined with respect to the example packer as follows:

W=2500 (28.35- 19.65) =2l,800 pounds (approximate) Knowing the actual longitudinal force to be imposed on the seal element to achieve a predetermined stress in the element, the difference between the cross-sectional area of the extrudahle material before extrusion and after extrusion is determined as follows:

A -a\ W/19,250 where:

A =the cross-sectional area of the extrudable material prior to extrusion, in square inches;

a =the combined cross-sectional area of the openings through the dies, in square inches;

W=the total longitudinal force on the seal element in pounds; and

19,250 is the approximate unit stress in. p.s.i. at which it has been determined that the lead material will extrude.

Applying this formula to the example packer the relationship between the extrudable material before and after extrusion is determined as follows:

A -a W/19,25-0=21,800/19,25( 1.13 square inches Therefore, in accordance with the above computations, the example packer, when using lead as the extrudable material and desiring to obtain 2,500 p.s.i. stress in the seal element, should have a lead charge which is 1.13 square inches larger before extrusion than it is after being extruded. Applying this to the embodiments of the invention disclosed herein, the single string packer shown in FIGURE 1 should have an annular lead charge and the annular space 7% within which it is disposed having a cross-sectional area 1.13 inches greater than the total cross-sectional area of the bores 81 of the die 72. With respect to the dual string packer element, the total crosssectional area of the lead charges 171 should be 1.13 square inches greater than the total cross-sectional area of the bores in the dies 164. By so sizing the dies and lead charges employed, the desired 2500 p.s.i. stress in the seal element should be obtainable in the disclosed packers when such packers are of the example dimensions. These sample computations may readily be applied to other extrudable materials and packers of other dimens1ons.

It will thus be seen that there has been described and illustrated a new and improved form of well tool with an expandible element for effecting a seal Within a well bore.

It will also be seen that the well tool includes a seal element which may be stressed to a predetermined value prior to locking within a well bore.

It will also be seen that the well tool is provided with a seal element which is expanded under a constantly increasing load and maintained under such load during the complete setting of the mechanism for setting the tool in a well bore.

It will additionally be evident that the well tool is provided with 'a seal element and setting mechanism which permits maximum stress to be induced in the seal element and maintained in the element without momentary relaxations of the element which would tend to result in a final setting of the slips with the seal element at a lower than maximum stress.

It will be further evident that the well tool employs an extrudable material as an integral link in the mechanism for expanding the seal element and setting the slips whereby the force on the seal element is steadily increased until a constant maximum force is exerted on the seal element at which time the material extrudes to permit final setting of the slips without relaxation of the force being exerted on the seal element.

It will also be evident that the well tool may be either of the single or multiple string type and uiilizes a material which is extrudable at a predetermined pressure as an integral link in the mechanism for setting the slips and expanding the seal element, the final expansion of the seal element and the setting of the slips being achieved at the force necessary to extrude the material through dies provided in the packers.

It will also be seen that the well tool includes a seal element which, after the tool is set and the seal element is laterally expanded, will withstand a pressure differential across the seal element greater than can be sustained by conventional forms of similar well tools.

It will be further seen that the well tool of the invention includes control means which permits stresses to be induced in the seal element during the setting of the tool which are in excess of the stresses normally obtainable in conventional forms of similar well tools.

It will also be seen that the well tool setting mechanism permits a predetermined stress to be built up in the seal element before the final set of slips can be expanded into engagement with the wall of a well bore.

It will additionally be seen that the well tool includes a seal element which is set under maximum stress conditions thus avoiding the necessity of additional stressing of the seal element subsequent to expansion of the slips thereby preventing the dragging of the slips against the inner wall of the casing of the well bore.

It will be further evident that there has been illustrated and described a well packer having upper and lower slips and an expandible seal element and that the upper slips are first set and the seal element is expanded to a predetermined stress limit prior to setting the lower slips to lock the seal element at such stress limit.

While lead has been disclosed as the preferred material to extrude through the die members of the packers, it will be evident that other materials may be employed to control the stress in the seal element and effect the final setting of the slips. For example, where lower stresses are required, the materials such as nylon, vinyl, rubber, or neoprene may be used.

If in a particular application of the packer, such as the packer illustrated in FIGURES l and 2, it is found that the cross-sectional area of the annular lead charge is too much greater than the total cross-sectional area of the die bores 74, the die bores may be effectively enlarged by substitution of a die having an annular opening therethrough thus making the areas of the die section and the lead charge and annular cylinder more nearly equal, This modification of the die member may be preferred to substitution of a material which is more easily extruded.

In lieu of extruding a solid material through a die for stressing the seal element and expanding the slips, apparatus may be provided for effecting the same result by forcing a liquid through a small orifice in pistons 164a movable in the cylinder 16% having oil or grease therein, the pistons each being provided with a back pressure regulator valve 190 or some other suitable releasable closure for controlling the passage of the liquid through the orifice to provide the necessary control to develop and maintain a desired back pressure for obtaining the required stresses in the seal element. Such a control assembly is shown in FIG- URE 8 wherein the piston 164:: has a cylindrical bore in which the regulatorvalve is movable longitudinally into and out of engagement of its tapered upper end seat 193 at its upper end with the downwardly facing seat 194 at the lower end of the orifice in the piston 164a into the cylinder. The valve is biased into engagement with the seat by a spring 191 which is adjustably confined between a flange 192 on the upper end of the valve and an adjusting bushing 195 having a lock nut 196 thereon threaded into the lower end of the bore of the piston 164a, whereby the valve is held against opening by the spring until the predetermined pressure load is applied to the liquid confined in the cylinder 160a therea bove, and maintains such predetermined pressure ditTerential across the orifice and the valve seat at the valve member during upward movement of the piston in the cylinder to maintain the pressure on the seal element of the packer while the lower slips are being moved upwardly to anchoring position on the lower slip cone.

While the invention has been described and illustrated in terms of well packers, it is to be understood that it applies to other forms of well tools which utilize expandible seal elements, such as bridge plugs. Also, the invention is applicable to well tools in which the lower slips are set first and the seal element is expanded with the upper slips being finally locked in place.

The foregoing description of the invention is explanatory only, and changes in the details of the construction illustrated may be made by those skilled in the art, within the scope of the appended claims, without departing from the spirit of the invention.

What is claimed and desired to be secured by Letters Patent is:

1. A well tool comprising in combination: body means; resilient seal element means secured around said body means adapted to be laterally expanded int-o sealing engagement with the wall of a well bore; locking means secured on said body means for locking said tool in a well bore; means associated with said seal element means for expanding said locking means; and means between the locking means and the seal element expanding means for expanding the seal element means to provide a predetermined stress upon said seal element means by movement of said locking means toward said seal element and, for continuously maintaining said predetermined stress upon said seal element means during actuation of said locking means to fully set locking position.

2. A well tool comprising in combination: mandrel means; resilient seal means engaged around said mandrel means and adapted to be stressed to effect lateral expansion for sealing an annular space around said mandrel means within a well casing; first slip-means engaged on said mandrel on one side of said seal means; second slip means engaged on said mandrel on the other side of said seal means; and means associated with said second slip means for resisting the setting of said second slip means until said seal means is stressed to a predetermined value, said means continuously maintaining said predetermined stress on said seal means throughout setting movement of said second slip means to set position.

3. A well tool comprising in combination: means comprising a mandrel having a central flow passage extending theret'hrough; laterally expansible resilient seal mean s engaged around said mandrel; first slip means supported on said mandrel on one side of said seal means; second slip means engaged on said mandrel 0n the other side of said seal means; and means operatively interconnecting said mandrel and said second slip means including means adapted to maintain a substantially rigid connection between said mandrel and said second slip means until a redctcrmincd force is exerts-d on said seal means by movement of said second slip means toward said seal means, said connecting means continuously maintaining said predetermined force on said seal means during movement of said second slip means to set position.

4. A well t-ool comprising in combination: means comprising a mandrel having a longitudinal flow passage extending therethrough; upper slip means engaged on said mandrel means; resilient seal means on said mandrel below said upper slip means, said seal means being adapted to be stressed to effect lateral expansion establishing a sealing relationship between said mandrel means and a well casing; lower slip means engaged on said mandrel below said seal means; and connecting means between said mandrel and said lower slip means for stressing said seal means and Setting said lower slips, said connecting means including means for rigidly coupling the slips and cone of said lower slip means to prevent setting of move ment of the lower slips until a predetermined stress condition has been effected in said seal means; and said coupling means being adapted to permit said lower slips to move to set position when said predetermined stress has been induced in said seal means and to maintain said predetermined stress in said seal means continuously throughout the setting movement of said lower slips to set position.

5. A well tool comprising in combination: mandrel means having a longitudinal flow passage extending therethrough; upper slip means engaged on said mandrel means; resilient seal means on said mandrel means be low said upper slip means, said seal means being adapted to be expanded laterally to elfect a seal between said mandrel means and the casing of a well bore; lower slip means engaged on said mandrel below said seal means; said upper slip means and said lower slip means functioning upon relative movement toward each other to longitudinally stress said seal means to effect lateral expension of said seal means; and coupling means for interconnecting said mandrel with said lower slip means and with said seal means, said coupling means including cylinder and piston means having a material in said cylinder resisting movement of said piston means with respect to said cylinder to impose a predetermined force on said seal means upon movement of said lower slip means toward said seal means by said mandrel and adapted to be actuated by longitudinal movement of said mandrel to displace said material from said cylinder means when said predetermined force is exerted between said mandrel and said lower slip means for freeing said lower slips to per mit them to be set when a predetermined stress has been induced in said seal means by said predetermined force, said coupling means maintaining said predetermined force and predetermined stress in said seal means continuously during movement of said lower slip means to expanded set position.

6. A well tool comprising in combination: a mandrel having a longitudinal fiow passage extending therethrough; an upper slip assembly engaged on said mandrel; a laterally expandable flexible seal element engaged on said mandrel below said upper slip assembly, the upper end of said seal element being adapted to engage the lower end of said upper slip assembly during expansion of said seal element; a lower slip assembly engaged on said mandrel below said seal element, the upper end of said lower slip assembly being adapted to engage the lower end of said seal element for forcing said lower end upwardly to effect lateral expansion of said seal element; said lower slip assembly being provided with a cylinder and a member movable in said cylinder and engageable with a material in said cylinder which restrains movement of said member in said cylinder whereby movement of said lower slip assembly toward said seal element etlects lateral expansion of said seal element with a predetermined force, said member in said cylinder being adapted to move in said cylinder to displace said material from said cylinder when a predetermined force is exerted between said member and said cylinder, said member and said cylinder functioning in combination with said material in said cylinder to couple the lower slips and lower cone of said lower slip assembly together to prevent movement of said lower slips with respect to said cone until said predetermined force is exerted between said member and said cylinder and to uncouple said lower slips from said lower cone when said predetermined force is exerted on said material in said cylinder to extrude the same from the cylinder permitting relative movement between said member and said cylinder to first stress said seal element to a predetermined value and then set said lower slips while constantly maintaining said predetermined force on said seal element.

7. A well tool comprising in combination: a mandrel having a longitudinal flow passage extending therethrough; an upper slip assembly engaged on said mandrel; a seal element adapted to expand laterally engaged on said mandrel below said upper slip assembly, the upper end of said seal element being engageable with the lower end of said upper slip assembly for eifecting lateral expansion of said seal element; a lower slip assembly engaged on said mandrel below said seal element, the upper end of said lower slip assembly being engageable with the lower end of said seal element for exerting a longitudinal force on said seal element to effect lateral expansion of said element; and said lower slip assembly including a first member having a cylinder formed therein and a second member slidable in said cylinder; means providing constant predetermined resistance to movement of said second member in said cylinder to apply a predetermined force on said seal means, said means in said cylinder being extrudable therefrom by said second member upon the application of said predetermined force thereto to maintain a predetermined stress in said seal element while said lower slip assembly is being moved to set locking position.

8. A well tool comprising in combination: a mandrel having a longitudinal flow passage extending therethrough; an upper slip assembly engaged on said mandrel; a resilient seal element positioned on said mandrel below said upper slip assembly, the upper end of said seal element being engageable with the lower end of said upper slip assembly for eltecting lateral expansion of said seal element; a lower slip assembly engaged on said mandrel below said seal element, the upper end of said lower slip assembly being engageable with the lower end of said seal element for applying a longitudinal force to said seal element to effect lateral expansion of said seal element; said lower slip assembly including means providing a cylinder and a die member carried by said mandrel, said die member and said cylinder being operatively associated with said die member slidably disposed in said cylinder for movement longitudinally therein; a relatively solid extrudable material in said cylinder between said die member and said cylinder and resisting movement of said die member into said cylinder with a predetermined force, whereby movement of said lower slip assembly toward said mandrel applies a predetermined force on said seal assembly distorting the same toward expanded position, said extrudable material being extrudable upon application of a force in excess of said predetermined force to permit said lower slip assembly to move to set gripping position while maintaining said predetermined stress on said seal element.

9. A well tool comprising in combination: a mandrel provided with a longitudinal flow passage extending therethrough; an upper slip assembly engaged on said mandrel; a seal element positioned around said mandrel below said upper slip assembly, the upper end of said seal element being engageable with the lower end of said upper slip assembly for efiecting lateral expansion of said element; a lower slip cone slidably positioned on said mandrel below said seal element, the upper end of said slip cone being engageable with the lower end of said seal element for forcing said seal element upwardly to effect lateral expansion of said seal element; a plurality of lower slips engaged around said lower cone and adapted to slide relative to said cone; an annular lower slip carrier operatively associated with said lower slips, said lower carrier having an internal longitudinal bore opening through the lower end thereof around and larger than said mandrel whereby an annular downwardly opening space is formed between said lower slip carrier and said mandrel; an annular shaped die member engaged in said annular downwardly facing bore of said mandrel and with the lower end of said lower slip carrier, said die member being provided with a die opening communicating with said annular space between said mandrel and said lower slip carrier; and the lower end of said lower slip cone extending into said annular space between said lower slip carrier and said mandrel, the lower end of said lower cone comprising a piston slidable within said annular space whereby relative movement between said lower slip carrier and said lower slip cone will effect relative movement of the lower end of said cone within said annular space; relatively solid deformable material disposed within said annular space between said die member and said piston and resisting movement of said die with respect to said piston during upward movement of said lower slip carrier until a predetermined force has been applied to the seal element by said lower slip cone, said extrudable material being then extrudable through said die to permit movement of said lower slips with respect to said lower slip cone to set position while maintaining a said predetermined force on said seal element.

It). A well tool comprising in combination: a mandrel having a longitudinal flow passage extending therethrough; an upper slip assembly engaged on said mandrel; a resilient seal element positioned around said mandrel below said upper slip assembly, said seal element being laterally expandable to effect a sealing relationship between said mandrel and the wall of a well casing, the upper end of said seal element being engageable with the lower end of said upper slip assembly; a lower slip cone slidably engaged on said mandrel below said seal element; a lower slip carrier engaged around said mandrel, the upper end of said slip carrier being fitted over the lower end of said lower cone and the inner surface of said slip carrier being spaced apart from said mandrel to form an annular cylinder around said mandrel encompassing the lower end of said lower cone; an annular die member engaged with the lower end of said mandrel and said lower slip carrier forming a substantially rigid connection be tween said mandrel and said lower slip carrier whereby movement of said mandrel effects corresponding movement of said lower slip carrier; said die member being provided with at least one die opening extending longitudinally therethrough from the lower end of said member into said annular cylinder between said mandrel and said lower slip carrier; an annular piston slidably positioned within said annular cylinder and engageable with the lower end of said lower slip cone whereby relative movement between said lower slip cone and said lower slip carrier effects movement of said annular piston within said annular cylinder; and a material in said annular cylinder between said die member and said piston resisting movement of said piston toward said die member in said cylinder with a predetermined force to effect movement of said seal means to expanded sealing position upon upward movement of said lower slip carrier relative to said seal member, said material in said cylinder being extruded through said die member by said piston to maintain said predetermined force on said seal means during setting of said lower slips.

11. A well tool comprising in combination: a mandrel having a longitudinal flow passage extending therethrough; an upper slip assembly on said mandrel, said slip assembly including an upper slip carrier and an upper slip cone, said carrier and said cone each being connectable to said mandrel by a shear pin; a resilient seal element positioned around said mandrel below said upper slip assembly, the upper end of said seal element being engageable .with the lower end of said upper slip cone for effecting lateral expansion of said seal element to form a seal between said mandrel and the wallof a well casing; a lower slip cone engaged around said mandrel below said seal element, said lower slip cone being slidable relative to said mandrel and adapted to engage on the upper end thereof the lower of said seal element to cooperate with said upper slip cone to impose a longitudinal force on said seal element for effecting lateral expansion of said element; said lower slip cone having a downwardly and inwardly sloping surface for expanding lower slips and a cylindrical external surface extending from the lower end of said cone concentric with the bore of said cone and connecting with said sloping surface; a lower slip carrier engaged around said mandrel, the upper end of said slip carrier fitting over and being slidable around the cylindrical lower portion of said lower slip cone, said lower slip carrier having an enlarged bore extending over a substantial portion of the length thereof and opening to the lower end of said slip carrier, the inner surface and upper end of said bore cooperating with the external surface of said mandrel to define an annular cylinder around said mandrel within said lower slip carricr encompassing the lower end of said lower slip cone; an annular die member engaged with and between the lower ends of said mandrel and said lower slip carrier, said die member being provided with a plurality of longitudinal die openings communicating with said annular cylinder and extending through the lower end'of the die member; an annular piston slidable disposed within said annular cylinder and engageable with the lower end of said lower slip cone whereby longitudinal movement of the lower slip cone and said lower siip carrier relative to each other will effect movement of said annular piston within said annular cylinder; a plurality of lower slips engaged around said lower slip cone and said lower slip carrier and adapted to be moved by said carrier along said sloping surface of said cone for expanding said slips; and means in said cylinder between said piston and said die member resisting movement of said slip carrier toward said cone with a predetermined force, whereby said seal element is moved to expanded position by such force, said means being movable from within said cylinder through said die member by said piston when the force applied to said means exceeds said predetermined force while maintaining said predetermined force on said seal element.

, 12. A well tool comprising in combination: a plurality of mandrels each having a longitudinal flow passage extending therethrough; an upper slip assembly engaged on said mandrels; a seal element around said mandrels below said upper slip assembly, said seal element being adapted to be stressed longitudinally to effect lateral expansion for sealing between said mandrels and the wall of a well casing; a lower slip cone engage-d around said mandrels below said seal assembly, the upper end of said lower slip cone being engageable with the lower end of said seal element for applying a longitudinal force to said seal element to effect lateral expansion of said element, said lower slip cone being provided with at least one cylinder located on each side of said mandrels and opening through the lower end of said cone; a lower slip carrier engaged around said mandrels below said lower slip cone, said carrier having at least one bore therethrough positioned on each side of said mandrels and corresponding to said cylinders in said lower slip cone; piston means having orifice means and flow control means controlling flow through said orifice means secured in each of said bores in said lower slip carrier and extending upwardly from said carrier into the corresponding cylinder in said lower slip cone and movable therein whereby relative movement of said lower cone and said lower carrier toward each other causes each piston means to be moved into the corresponding cylinder; a plurality of lower slips engaged around said mandrel on said lower slip carrier and adapted to be moved in relation to said lower cone to effect outward expansion of said slips to gripping position; and means in each of said cylinders above said piston means resisting movement of said piston means in said cylinder bores with a predetermined force to cause ap plication of a predetermined expanding stress on said seal member, said means being displaceable from said bores through said piston means upon application of a force thereto in excess of said predetermined force to permit said slips to move to gripping position while maintaining said predetermnied force on said seal means.

13. A well tool comprising in combination: at least two mandrels positioned substantially parallel to each other, each of said mandrels having a longitudinal flow passage extending therethrough; a head member engaged on the upper ends of said mandrels, said head member being provided with a plurality of longitudinal bores, a bore being provided for cooperating with the flow passage through each of said mandrels; an upper slip assembly engaged on said mandrels below said head member; at least one shear pin connected between said upper slip assembly and said mandrels; a resilient seal element positioned around said mandrels below said upper slip assembly, the upper end of said seal element being engageable with the lower end of the slip cone of said upper slip assembly, said resilient seal element being expandable laterally in response to longitudinal forces on the ends of said seal element forcing said ends toward each other; a lower slip cone positioned around said mandrels below said seal element, said lower slip cone being slidable relative to said mandrels, the upper end of said slip cone being engageable with the lower end of said seal element for applying a longitudinal force on the lower end of said seal element, said lower cone having formed therein and opening through the bottom thereof at least two cylindrical chambers, said chambers being spaced apart from each other and located on opposite sides of said mandrels; a lock ring secured on each of said mandrels to engage said lower slip cone for limiting the relative movement between said lower slip cone and said mandrels; a lower slip carrier engaged around said mandrels below said lower slip cone and restrained from longitudinal movement relative to said mandrels, said lower slip carrier having at least two longitudinal bores spaced apart from each other and positioned on opposite sides of said mandrels, each of said bores corresponding with one of said cylinders in said lower cone; a die secured in each of said bores in said lower slip carrier and extending upwardly from said carrier, each of said dies being movable into the cylinder in the lower slip cone corresponding to the bore in said lower carrier in which said die is secured whereby upward movement of said lower slip carrier will cause said die to be moved into the cylinder in said lower slip cone; means including a lock ring securing said lower slip carrier to said mandrels and preventing longitudinal movement of said carrier relative to said mandrels; a plurality of slips engaged around said lower slip carrier and adapted to be moved upwardly along said lower slip cone for effecting outward expansion of said slips by relative movement toward each other of said lower slip cone and said lower slip carrier; means in each of said cylinders in said lower slip cone above each of said dies resisting movement of said dies in said cylinders with a predetermined force whereby upward movement of said slip carrier toward said slip cone impresses a predetermined force on said seal means to move the same toward expanded position, said means in said cylinder being extrudable therefrom through said dies upon application of a force thereto in excess of said predetermined force to permit said slips to move to set gripping position while maintaining said predetermined force on said seal means.

14. A well tool in accordance with claim 13 wherein said material within said cylinders is a relatively solid deformable material.

l 15. A well tool comprising in combination: a mandrel having a longitudinal bore extending therethrough; a head member engaged on the upper end of said mandrel for connecting said tool to a running tool; an upper slip assembly engaged around said mandrel below said head member; at least one shear pin engaged between said slip assembly and said mandrel; a resilient seal element around said mandrel below said upper slip assembly, the upper end of said seal element being engageable with the lower end of the cone of said upper slip assembly, said seal element being adapted to be expanded laterally in response to forces applied to opposite ends of said seal element pushing said ends toward each other; a lower slip cone slidably engaged around said mandrel below said seal element, the upper end of said lower slip cone being engageable with the lower end of said seal element for forcing said lower end of said seal element upwardly to effect lateral expansion of said seal element, said lower cone having an enlarged longitudinal bore over a section opening through the upper end of said bore, the lower end of said enlarged bore forming a shoulder cooperating with a shoulder formed around the said mandrel to limit the sliding relationship between said lower cone and said mandrel, said lower cone being provided with a downwardly and outwardly sloping surface. along the central portion thereof and a substantially cylindrical surface concentric with the central bore of said cone extending along the lower portion of said cone connecting with said sloping surface on said cone; a lower slip carrier engaged around said mandrel and the lower portion of said lower slip cone, said lower slip carrier being spaced apart from both said mandrel and the lower cylindrical portion of said lower cone over a major portion of the length of said lower slip carrier thereby forming an annular cylinder around both said mandrel and the lower portion of said lower cone, a portion of the upper end of said lower slip carrier extending inwardly to fit in sliding relationship around said lower slip cone forming an upper end for said annular cylinder within said lower slip carrier; an annular piston positioned within said annular cylinder and operatively engaged with the lower end of said lower slip cone whereby relative movement between said lower slip carrier and said lower slip cone will effect movement of said annular piston within said annular cylinder; an annular die threadedly engaged with the lower end of said lower slip carrier and said mandrel, said die having longitudinal die openings extending through said die from said annular cylinder through the lower end of said die whereby material in said annular cylinder may be dis placed from said annular cylinder through said die by said annular piston; a plurality of lower slips engaged on said lower slip carrier around said lower slip cone; and a charge of relatively solid deformable material within said annular cylinder resisting movement of said piston toward said die in said cylinder whereby movement of said lower slips toward said lower slip cone imposes a predetermined stress on said seal means, said material being extrudable through said die to permit said lower slips to move to set position while maintaining said predetermined force on said seal means.

16. A well tool in accordance with claim 15 wherein said material restraining movement of said piston in said cylinder consists of lead.

17. A well tool comprising in combination: a mandrel; a resilient seal element positioned around said mandrel and adapted to be stressed to effect lateral expansion; an upper slip assembly engaged on said mandrel above said seal element; a lower slip assembly engaged on said mandrel below said seal element; and means associated with said mandrel, said lower slip assembly and said seal element providing for application of a continuous predetermined force to said seal element for stressing the same to expanded position upon movement of said lower slip assembly toward said seal element and providing for continuous application of such constant force to said seal References Cited UNITED STATES PATENTS Urbanosky 166--135 X Rhea.

Lawrence 16698 Davis et a]. 166134 X 20 Bigelow 166--134 Baker 166134 X Sizer 166212 X Conrad 166134 CHARLES E. OCONNELL, Primary Examiner.

JACOB L. NACKENOFF, .Examiner. I. A. CALVERT, Assistant Examiner. 

